Process for forming a sheet of material

Abstract

A process for forming a homogeneous sheet from particulate elements, (as herein defined), at least some of which have an inherent vertical mobility (as herein defined) in water at normal temperature and pressure of from about 1 to about 21 cms/sec, which comprises the steps of forming a foamed dispersion of said particulate elements, and depositing and draining said dispersion on a foraminous support.

What is claimed is: 
     
       1. A process for forming a homogeneous sheet from particulate elements at least some of which have an inherent vertical mobility in water at normal temperature and pressure of from about 5 to about 21 cms/sec, which comprises the steps of forming an aqueous foamed dispersion of said particulate elements, and depositing and draining said dispersion on a foraminous support. 
     
     
       2. A process as claimed in claim 1 in which said particles have vertical mobilities of not more than about 13 cms/sec. 
     
     
       3. A process as claimed in claim 1 in which said particulate elements comprise metallic particles. 
     
     
       4. A process as claimed in claim 1 in which a plurality of kinds of particulate elements are included and which have different inherent vertical mobilities. 
     
     
       5. A process as claimed in claim 4 in which the particulate elements comprise a mixture of elements which rise and elements which settle in water. 
     
     
       6. A process as claimed in any one of the preceding claims 1 to 5 in which the foamed dispersion is aqueous and has a viscosity of at least 22 second when measured by Form Cup Type B-4 at 20° C. according to British Standard No. BS1733 or an equivalent viscosity as determined according to British Standard BS3900-A6. 
     
     
       7. A process as claimed in any one of claims 1 to 5 in which the foamed dispersion has an air content of at least 55% and is comprised of bubbles having an average size of 0.2 mm. 
     
     
       8. A process as claimed in claim 7 in which the foamed dispersion has an air content of at least about 65%. 
     
     
       9. A sheet formed by the process set forth in any one of the claims 1 to 5.